There is great desire to incorporate photon-counting detectors also known as energy discriminating X-ray detectors in computed tomography (CT). The photon-counting detectors have some potential to improve image quality, reduce dose and enable new clinical applications of CT. The photon-counting detectors acquire data including extra spectral information for providing material classification, improving quantitative imaging and reducing beam-hardening artifacts.
Despite the above advantages over widely used energy-integrating detectors, the photon-counting detectors have certain disadvantages. The photon-counting detectors are generally limited by the high costs and their count-rate. Furthermore, although the signal-to-noise ratio (SNR) in the photon-counting detectors is reduced at low flux levels for a small pixel size, the photon-counting detectors experience an increased level of inter-pixel interference due to the small pixel size. On the other hand, the photon-counting detectors such as CdTe/CdZnTe sensors have poor performance at high flux levels, and consequently the SNR deteriorates. For these reasons, the photon-counting detectors have not yet replaced the energy-integrating detectors currently utilized in clinical CT systems.
Because of the above described issues of the photon-counting detectors, a dual-tube CT system has been proposed to utilize a combination of photon-counting detectors and integrating detectors. In one exemplary dual-tube CT system, one source projects X-ray towards a photon-counting detector while the other source projects X-ray towards a conventional detector that is placed at a predetermined angle with respect to the photon-counting detector. In order to cope with the high flux rates used in the exemplary dual-tube CT system, the pixel-size of the photon-counting detector was made substantially small, but charge sharing and K-escape rates have been increased to a point where the above described advantages of the photon-counting detector have substantially diminished.
Because of the above described prior art, there remains a desire to improve CT imaging using photon-counting detectors without suffering from the known disadvantages such as the high cost and the low sampling rate.